CN113740649A - Method for verifying differential protection ratio braking coefficient K value of transformer protection device - Google Patents
Method for verifying differential protection ratio braking coefficient K value of transformer protection device Download PDFInfo
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Abstract
The invention discloses a method for verifying a differential protection ratio braking coefficient K value of a transformer protection device, and belongs to the field of transformer protection. According to different brake current and differential current values in a selected action area, corresponding high-voltage side current values and low-voltage side current values can be directly and quickly calculated, the result is input into a protection tester, the high-voltage side current A phase is taken as a variable, the amplitude value is 0.05A, the variable is adjusted to be decreased progressively, and after differential protection action, the differential current and the brake current values displayed in the device at the moment are recorded; and calculating and verifying whether the differential braking coefficient K can meet the requirement or not through at least three groups of test data. The invention overcomes the problems of complicated check calculation and easy error of the differential protection ratio brake coefficient in the prior art, can simply and efficiently obtain test data, can finish the check work of the differential protection ratio brake coefficient K value by inputting the corresponding data into a protection tester, and saves the protection check time.
Description
Technical Field
The invention relates to the technical field of transformer protection, in particular to a method for verifying a differential protection ratio braking coefficient K value of a transformer protection device.
Background
The equipment maintenance is carried out every year in power generation enterprises, a large number of large-capacity factory-used low-voltage transformers are involved in differential protection of low-voltage equipment of a unit, such as 6kV equipment, the detection of the differential protection rate braking coefficient K value needs a large amount of calculation data and is complex in algorithm, the algorithm is carried in according to the given algorithm of the device specification, a large amount of manpower and time are wasted, a little tiger is prone to calculation errors, and a lot of inconvenience is brought to production practice.
Through retrieval, the Chinese patent application number: 2017101748210, the name of invention creation is: the application discloses a main transformer protection ratio brake coefficient simulation verification method and device, which are used for carrying out main transformer protection ratio brake coefficient simulation verification from three sides of a transformer according to 3 currents provided by a static tester, and solving the technical problem that the existing debugging method is difficult to carry out main transformer protection ratio brake coefficient simulation verification from three sides of the transformer when the static tester can only provide 3 currents.
As another example, application No. 201911009527X discloses a method for testing the braking characteristics of a transformer differential protection ratio, wherein an electrical device has a relay protection device, and a current longitudinal differential protection device has a differential circuit high-voltage side and a differential circuit low-voltage side, and the method comprises the following steps: selecting a high-voltage side of a differential circuit and a low-voltage side of the differential circuit, wherein the rated current Ieh of the high-voltage side of the transformer is 1 ampere, and the differential current threshold value Icd is set to be 0.5 ampere; the method of the application can be popularized to the transformer longitudinal differential protection of other types with the same current phase compensation mode, and can also provide reference for the inspection of the transformer ratio differential protection of different current phase compensation modes. The above applications all relate to the optimization of the testing technology for the braking coefficient of the differential protection, but in practice, richer, more convenient and efficient testing modes are needed, and different conveniences are provided for popularization and application.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to solve the problems of complex verification and calculation and easy error of the differential protection ratio braking coefficient in the prior art, and provides a method for verifying the differential protection ratio braking coefficient K value of the transformer protection device.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
the invention discloses a method for verifying a differential protection ratio braking coefficient K value of a transformer protection device, which comprises the following steps:
s1, determining the original calculation mode of the differential current and the braking current according to the wiring mode of the transformer;
s2, setting the A phase current value of the high-voltage side of the transformer to be X, the a phase current and the c phase current of the low-voltage side of the transformer to be equal in magnitude and the value to be Y, and substituting the positive sequence into the calculation mode in S1 to obtain the relation between X, Y and the differential current and the braking current; x, Y values can be obtained according to the corresponding values of the differential current and the braking current; in this way, B, C-phase current values can be obtained;
s3, selecting different brake current and differential current values in the action area according to S2 to obtain corresponding high-voltage side current values and low-voltage side current values, inputting the result into a protection tester, adjusting the variable to be decreased by taking the phase A of the high-voltage side current as a variable and taking the amplitude value of the high-voltage side current as 0.05A, and recording the differential current and the brake current values displayed in the device at the moment after differential protection action; and verifying whether the differential braking coefficient K meets the requirement or not through at least three groups of test data.
Furthermore, the connection mode of the low-voltage transformer in S1 is D, yn11, the number of transformer clock points is D, yn11, and the original calculation of the differential current and the braking current is:
wherein: DIa、DIb、DIc: differential currents of three phases of the transformer A, B, C;
HIa、HIb、HIc: braking currents of three phases of the transformer A, B, C respectively;
Iah、Ibh、Ich: a, B, C three-phase currents on the high-voltage side of the transformer respectively;
Ial、Ibl、Icl: a, B, C three-phase currents on the low-voltage side of the transformer respectively;
furthermore, in S2, taking the phase a on the high-voltage side of the transformer as an example, the phase a current value on the high-voltage side of the transformer is set to be X, the two phases of currents on the low-voltage sides a and c have equal magnitudes, and the value is Y, and the positive sequence is substituted into the formula one, and since the high-voltage side and the low-voltage side of the transformer in the protection device are connected by 180 degrees, the absolute value of the side die on the high-voltage side is positive, and the die is negative, the following can be obtained: HI (high-intensity)a＝(X+KphlY)/2；DIa＝-X+KphlY; and a fifth formula.
Further, in S2, if the braking current is 0.5Ie-3IeGet HIa＝2IeThen differential current DIa＝Icdqd+K(2Ie-0.5Ie)＝0.5Ie+K*1.5IeK is a known set value, HIa、DIaSubstituting the formula into a fifth formula, namely solving and obtaining a phase A current value X of the high-voltage side of the transformer and a two-phase current value Y of the low-voltage side a and the low-voltage side c; by this method, B, C phase current can be obtained, and braking current and differential current values in different ranges can be calculated.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) according to the method for verifying the differential protection ratio brake coefficient K value of the transformer protection device, the corresponding high-voltage side current value and the low-voltage side current value can be directly and quickly calculated according to different brake currents and differential current values in a selected action area, the result is input into a protection tester, the high-voltage side current A phase is taken as a variable, the amplitude is 0.05A, the variable is adjusted to be decreased gradually, and after differential protection action, the differential current and the brake current value displayed in the device at the moment are recorded; whether the differential braking coefficient K can meet the requirements or not is calculated and verified through at least three groups of test data, the effect is obvious, the verification time is greatly shortened, the verification accuracy is improved, the technical requirements on inspectors are also reduced, and the method is suitable for popularization and application.
Drawings
FIG. 1 is a schematic diagram of the differential protection operation of the protection device of the present invention;
wherein Icdqd: a ratio differential protection minimum starting current setting value A;
Ie: running a rated current secondary value, A, of the transformer;
Isd: a ratio differential protection quick-break current setting value A;
k: a rate braking coefficient;
DI: differential current, A;
HI: a braking current, A;
FIG. 2 is a logic diagram of the differential protection operation of the present invention;
wherein Icdqd: a ratio differential protection starting current setting value A;
Ie: running a rated current secondary value, A, of the transformer;
k: a rate braking coefficient;
DI: differential current, A;
HI: braking current, a.
Detailed Description
For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The present invention will be further described with reference to the following examples.
Example 1
In the method for verifying the braking coefficient K value of the differential protection ratio of the transformer protection device of the embodiment, firstly, the differential protection principle and the action logic of the protection device are explained, and as shown in fig. 1, a corresponding differential protection action principle diagram is given for a specific protection device in production practice; fig. 2 is a logic block diagram of the differential protection operation of the protection device. The protection can reliably act in the action area and can be reliably locked in the braking area. The differential current exceeding the differential protection snap-off constant value can protect against the locking of the braking current and must act reliably. All of which are well known in the industry and will not be described further herein. The purpose of this embodiment is also to verify whether the value of the braking coefficient of rate K meets the requirement of fixed value through multiple sets of data.
The verification method of the embodiment specifically comprises the following steps:
s1, determining the original calculation mode of the protection constant values of the differential current and the braking current according to the wiring mode of the transformer;
specifically, the wiring method of the low-voltage transformer in the general power plant is D, yn11, the number of transformer clock points is D, yn11, and the original calculation of the differential current and the braking current is:
wherein: DIa、DIb、DIc: differential currents of three phases of the transformer A, B, C;
HIa、HIb、HIc: braking currents of three phases of the transformer A, B, C respectively;
Iah、Ibh、Ich: a, B, C three-phase currents on the high-voltage side of the transformer respectively;
Ial、Ibl、Icl: a, B, C three-phase currents on the low-voltage side of the transformer respectively;
in practice, the corresponding K is also obtained based on known data given by the protection devicephlValues, different transformer parameters will result in KphlThe calculated values are different, and K can be calculated according to the parameter values required by the formula four-inputphlThe value is obtained.
Taking a working transformer of a power plant as an example, the equipmentThe parameters are as follows: capacity: 2500kVA, high side CT transformation ratio: 400/1, low side CT transformation ratio: 5000/1, rated voltage of the high-voltage side is 6.3kV, rated primary current of the high-voltage side is: 229.1A, high side rated secondary current, i.e. IeIt was 0.57A, and the low-side rated voltage was 0.4 kV. Protection constant value: differential quick-break current: 12IeMinimum operating current, i.e. IcdqdIs 0.5IeThe ratio brake coefficient K is 0.55, the second harmonic brake coefficient is 0.15, and differential protection is input.
Substituting the parameters into formula four to obtain the secondary edge transformation ratio coefficient Kphl＝0.4*5000/(6.3*400)＝0.79。
The criteria for the protection action are as follows:
in the formula Icdqd: a ratio differential protection action current setting value A;
Ie: running a rated current secondary value, A, of the transformer;
k: a rate braking coefficient;
DI: differential current, A;
HI: braking current, a.
S2, setting the A phase current value of the high-voltage side of the transformer to be X, the a phase current and the c phase current of the low-voltage side of the transformer to be equal in magnitude and the value to be Y, and substituting the positive sequence into the calculation mode in S1 to obtain the relation between X, Y and the differential current and the braking current; x, Y values can be obtained according to the corresponding values of the differential current and the braking current; in this way, B, C-phase current values can be obtained;
specifically, taking the phase a at the high-voltage side of the transformer as an example, the phase a current value at the high-voltage side of the transformer is set to be X, the two phases of currents at the low-voltage sides a and c are equal in magnitude, the value is Y, and the positive sequence is substituted into the formula one, and since the high-voltage side and the low-voltage side of the transformer in the protection device adopt 180-degree wiring, the absolute value of the side die at the high-voltage side is positive, and the die is negative, the following can be obtained:
HIa＝(X+KphlY)/2；DIa＝-X+Kphly; formula (II)And fifthly.
Further, the braking current is taken to be between 0.5Ie and 3Ie, and HI is takena＝2IeThe differential current DI can be calculated according to the differential schematic diagram in FIG. 1a＝Icdqd+K(2Ie-0.5Ie)＝0.5Ie+K*1.5IeContinuing with the example given above for a power plant operating transformer, IeIs 0.57A, K is a known given value of 0.55, KphlCalculated as 0.79, DIa＝1.325Ie(ii) a Mixing HIa＝2Ie、DIa＝1.325Ie(ii) a Substituting into equation five:
2Ie＝(X+0.79Y)/2＝1.14；
1.325Ie＝-X+0.79Y＝0.755；
the phase current value X of the A-phase of the high-voltage side of the transformer is 0.762; the two-phase current value Y on the low-voltage side a and c is 1.921.
By this method, B, C phase current can be obtained, and braking current and differential current values in different ranges can be calculated.
S3, selecting different brake current and differential current values in the action area according to the method to obtain corresponding high-voltage side current values and low-voltage side current values, inputting obtained result data into a protection tester, adjusting the variable to be decreased by taking the phase A of the high-voltage side current as a variable, wherein the amplitude value is 0.05A, and recording the differential current and the brake current values displayed in the device at the moment after differential protection action; and verifying whether the differential braking coefficient K meets the requirement or not through at least three groups of test data. By adopting the verification method of the embodiment, the effect is obvious, the verification time is greatly shortened, the calculation accuracy is improved, and the technical requirements on inspectors are also reduced.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (4)
1. The method for verifying the differential protection ratio braking coefficient K value of the transformer protection device is characterized by comprising the following steps of: the method comprises the following steps:
s1, determining the original calculation mode of the differential current and the braking current according to the wiring mode of the transformer;
s2, setting the A phase current value of the high-voltage side of the transformer to be X, the a phase current and the c phase current of the low-voltage side of the transformer to be equal in magnitude and the value to be Y, and substituting the positive sequence into the calculation mode in S1 to obtain the relation between X, Y and the differential current and the braking current; x, Y values can be obtained according to the corresponding values of the differential current and the braking current; in this way, B, C-phase current values can be obtained;
s3, selecting different brake current and differential current values in the action area according to S2 to obtain corresponding high-voltage side current values and low-voltage side current values, inputting the result into a protection tester, adjusting the variable to be decreased by taking the phase A of the high-voltage side current as a variable and taking the amplitude value of the high-voltage side current as 0.05A, and recording the differential current and the brake current values displayed in the device at the moment after differential protection action; and verifying whether the differential braking coefficient K meets the requirement or not through at least three groups of test data.
2. The method for verifying the braking coefficient K of the differential protection ratio of the transformer protection device according to claim 1, wherein: the wiring mode of the low-voltage transformer in S1 is D, yn11, the number of the transformer clock points is D, yn11, and the original calculation of the differential current and the braking current is as follows:
wherein: DIa、DIb、DIc: differential currents of three phases of the transformer A, B, C;
HIa、HIb、HIc: braking currents of three phases of the transformer A, B, C respectively;
Iah、Ibh、Ich: a, B, C three-phase currents on the high-voltage side of the transformer respectively;
Ial、Ibl、Icl: a, B, C three-phase currents on the low-voltage side of the transformer respectively;
3. the method for verifying the braking coefficient K of the differential protection ratio of the transformer protection device according to claim 2, wherein: in S2, taking the phase a on the high-voltage side of the transformer as an example, setting the phase a current value on the high-voltage side of the transformer to be X, the two phases of currents on the low-voltage sides a and c to be equal in magnitude, and the value to be Y, positive sequence, and substituting into formula one, and because the high-voltage side and the low-voltage side of the transformer in the protection device adopt 180-degree wiring, the absolute value of the high-voltage side mold is positive, and the mold is negative, the following can be obtained: HI (high-intensity)a＝(X+KphlY)/2；DIa＝-X+KphlY; and a fifth formula.
4. The method for verifying the braking coefficient K of the differential protection ratio of the transformer protection device according to claim 3, wherein: in S2, if the braking current is taken to be 0.5Ie-3IeGet HIa＝2IeThen differential current DIa＝Icdqd+K(2Ie-0.5Ie)＝0.5Ie+K*1.5IeK is a known set value, HIa、DIaSubstituting the formula five, the A phase current value X of the high-voltage side of the transformer and the a and c two-phase current values of the low-voltage side of the transformer can be solved and obtainedA value Y; by this method, B, C phase current can be obtained, and braking current and differential current values in different ranges can be calculated.
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Cited By (2)
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| CN114264901A (en) * | 2021-12-07 | 2022-04-01 | 广东电网有限责任公司 | Balance current simulation method and related device during transformer out-of-area fault |
| CN117612846A (en) * | 2023-10-26 | 2024-02-27 | 中建三局第三建设工程有限责任公司 | Transformer differential protection debugging system and method |
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